Experimental Testing Of Partially Encased Composite Beam Columns

Ehab M. Hanna Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 6, Issue 1, (Part - 3) January 2016, pp.64-71
www.ijera.com 64|P a g e
Experimental Testing Of Partially Encased Composite Beam
Columns
Ehab M. Hanna1
, Sameh M. Gaawan2
1
Ph.D. Department of Civil Engineering, Faculty of Engineering Mataria, Helwan University, Cairo, Egypt.
2
Ph.D. Associate Professor Department Of Civil Engineering Mataria, Faculty of Engineering, Helwan
University, Cairo Egypt.
Abstract
The past few decades have seen outstanding advances in the use of composite materials in structural
applications. There can be little doubt that, within engineering circles, composites have revolutionized
traditional design concepts and made possible an unparalleled range of new and exciting possibilities as viable
materials for construction.
In addition to the well-known advantages of composite columns, partially encased composite columns offered
simplified beam-to-column connection as well as reduced or omitted shuttering thus achieved more cost
effective construction. Some companies have patented these new types of partially encased composite column
made of light welded steel shapes; moreover, the Canadian Institute of Steel construction CISC has recognized
and codified this type of columns.
In This paper, Partially Encased Composite Beam Columns is introduced; experimental studies are made on five
partially encased beam columns to investigate the behavior of eccentrically loaded partially encased composite
columns using different parameters.
Database subject headings: Composite, columns, encased, partially, equation, steel, slender, plates.
I. Background
The partially encased composite beam columns
(PECBC) configuration described in this paper is a
relatively recent development in composite structures
consisting of thin walled, welded H-shaped steel
section with concrete infill cast between the flanges
as shown in Figure 1. Transverse links are provided
between the flanges at regular intervals to improve
the resistance to local buckling. This new composite
system was developed to overcome the limitations
related to erection, connection design, and economy
of more commonly used composite beam column.
Studies about this new beam column system were
limited; Brent S. Pricket and Robert G. Driver (2006)
studied the behavior of partially encased composite
columns made with high performance concrete some
of the test specimens were loaded under eccentric
loading; Mahboba Begum, Robert G Driver and Alaa
E Elwi (2007) studied finite element modeling of
partially encased composite columns using dynamic
explicit method, eccentrically loaded specimens were
modeled with different link spacing and load
eccentricities and either with or without longitudinal
reinforcement.; Saima Ali & Mahboba
Begum (2011) studied the behavior of partially
encased slender composite columns in eccentric load;
and Christine La Casse (2011) made an experimental
and analytical study for PECC using high
performance concrete and fiber concrete seven
specimens were tested under axial compression and
flexure; the failure has been initiated either by the
simultaneous compressive crushing of the concrete
and the local buckling of the steel flanges or by
compressive crushing of the concrete followed by the
local buckling in the post-peak range.
II. Objective and Scope of this study
The main objective of this study is to check the
behavior and strength of PECBC, using experimental
approach along with nonlinear finite element
modeling using Cosmos / M program; to investigate
the behavior of these eccentrically loaded columns
through different parameters.
Three series were examined; series I used to
examine the PECBC while series II to examine bare
steel beam column and series III to examine
reinforced concrete columns. All three series had the
same geometric and strength characteristics.
Then a comparison of the ultimate load carrying
capacity of the three types of columns was made to
know the advantages of the new introduced PECBC
against the traditional types of steel or reinforced
concrete beam columns.
RESEARCH ARTICLE OPEN ACCESS

Figure (1) Typical PECBC Illustration
III. Test Program
Five PECBC measuring 100x100 in cross section
were constructed as shown in Table 1; three of them
with height 500mm; one of height 800mm and one of
height 1000mm. H- Steel plates used with thickness
2mm; the flange width-to-thickness ratio for the
columns was 25. Two different link spacing were
used to study the effect of link spacing on column
behavior. Link diameter of 6mm was used. The links
are set back form the flange tips so that there is
20mm of clear concrete cover between the link and
the concrete face. Four columns were cast with
concrete of strength (350 kg/m2) and one was cast
with concrete strength (300 kg/m2). The end zone of
the columns (100mm of column length at each end)
was strengthened to prevent possible failure at these
locations due to uneven loading. Additional links
were added so that the link spacing was 50mm for the
first 100mm of the end zone as shown in Figure (1).
Test specimens P1 through P5 were designed to
examine the behavior of eccentrically loaded PEC
columns. Three Parameters were tested 1- Links
spacing. 2- Concrete compressive strength. 3-
Column height to depth ratio. P1 was the datum
specimen P2 was used to examine the effect of link
spacing as it had link spacing equal to half column
depth while the other specimens with ink spacing
equals column depth. P3 was used to examine the
effect of concrete strength as it had strength of 300
Kg/cm2 while the other specimens, had concrete
strength of 350 Kg/cm2. P4 & P5 were used to
examine the effect of column height parameter and
the effect of height to depth ration as P4 had height to
depth ratio of 8 while P5 had height to depth ratio of
10, while P1 through P3 had height to depth ratio of
5.
Four strain gauges and two linear potentiometers
are connected to each column as marked below in
Figure (2).
Figure (2) Strain gauges and linear potentiometers
numbering
Columns P-1
Specimen P-1 is used to study the effect of the
eccentric loading on the behavior of PECBC.
Loading was applied and increased gradually from 5
tons up to 20 tons; meters readings and observations
are recorded every 5 ton.
Table 1. Specimens Properties
Then load is increased from 23 tons to 40 tons gradually; readings and observations are recorded every 2 tons;
when reaching 30 tons traces of buckling of column flange is observed at the rear side 140 mm from column top
(0.3H) with traces of cracks at the column top; at 32 tons; buckling of column flange in the same location
increases; and concrete crakes are observed at the column top. The Column buckling starts at 30 tons Load; and
0.75 m.t bending moments; accordingly the failure load is 30 tons and the failure mode is buckling of flange
plates associated with concrete crushing; similar to Tremblay et al. (1998). Buckling happened right after the
link spacing confinement; and when buckling happens the steel plate leaves the concrete surface thus the
Specimen 2b (mm) d (mm) T (mm) S (mm) E (mm) H (mm) fcu (Kg/cm2) Fy (Kg/cm2)
P-1 100 100 2.0 100 25 500 350 2350
P-2 100 100 2.0 50 25 500 350 2350
P-3 100 100 2.0 100 25 500 300 2350
P-4 100 100 2.0 100 25 800 350 2350
P-5 100 100 2.0 100 25 1000 350 2350

confinement of the concrete no longer exists thus the concrete acts alone and cracks appear. By increasing the
load the buckling increases and appears in different location of the flange as shown in Figure (3) and the cracks
of the concrete appear everywhere as shown in Figure (4); when removing the cracked concrete the web plate
also has buckled as shown in Figure (5).
Columns P-2
Specimen P-2 is used to study the effect of the first parameter closer link spacing (s=d/2). Loading was applied
and increased gradually from 5 tons up to 20 tons; readings and observations are recorded every 5 ton; then load
increased from 22 tons to 36 tons gradually; readings and observations are recorded every 2 tons. Up to 30 ton
loading there are no observations of any flange buckling or concrete crushing. At 32 ton load traces of buckling
of column flange is observed at the front side 250 mm from column top (0.5H) at the right side and at the
bottom from the left side; along with traces of concrete cracks at column top. Column buckling starts at 32 tons
Load; and 0.8 m.t bending moments; accordingly the failure load is 32 tons and the failure mode is buckling of
flange plates associated with concrete crushing; similar to Tremblay et al. (1998).
The failure load is 2 tons higher than specimen P-1 and this is due to the closer link spacing used; thus closer
link spacing enhances the column load capacity and failure mode. Flanges buckling and concrete cracks
happened at column mid height Figure (6) & (7).
The column failure zones indications is marked out on the column showing flange plate buckling zone and
concrete failure zones Figures (8).
Columns P-3
Specimen P-3 is used to study the effect of the second parameter the different concrete compressive strength
(300 Kg/cm2). Loading was applied and increased gradually from 2 tons up to 38 tons; readings and
observations are recorded every 2 ton. Up to 26 ton loading there are no observations of any flange buckling or
concrete crushing. At 28 ton load separation between the concrete face and the flange plate at the right side at
mid height of column is observed. At 30 ton; column flange buckling occurred at height of 330 mm (0.66H)
from column top at the right side. Buckling continued to increase at this location up to 34 ton. The column
buckling starts at 28 tons load; and 0.7 m.t bending moments; accordingly the failure load is 28 tons and the
failure mode is buckling of flange plates associated with concrete crushing. The failure load was 2 tons less than
specimen P-1and the failure in both columns is due to buckling of flange plates; but it is obvious that the failure
load decreased because of using lower concrete compressive strength thus lower confinement of the concrete to
the steel flange plates thus faster buckling; also the failure load was less by 4 tons than specimen P-2 and this is
due to the using larger link spacing and less concrete compressive strength. The separation between the concrete
and the flange plates happened at the column mid height at the right side of the column Figure (9) (the same side
where the load is applied) and the buckling happened at the same side but at 0.66 of the column height Figure
(10); this separation is due to the using of lesser concrete compressive strength; this separation made the
buckling happed faster than column P-1 or P-2 accordingly lesser column capacity. When buckling happens the
steel plate leaves the concrete surface thus the confinement of the concrete no longer exists thus concrete acts
alone and cracks appears Figure (11); in this specimen after appearance of flange buckling and of concrete
cracks; test continued up to 34 tons and then stopped.
Columns P-4
Specimen P-4 is used to study the effect of the third parameter the column height to depth ratio (H/d = 8) on the
behavior of partially encased composite column under the effect of eccentric loading.
Load was applied and increased gradually from 5 tons up to 15 tons; readings and observations are recorded
every 5 ton. Then loads was increased from 15 tons to 25 tons gradually; readings and observations are recorded
every 2 tons. Up to 23 ton loading there are no observations of any flange buckling or concrete crushing. At 25
ton load; column flange buckling occurred at height of 300 mm (0.375H) from column top at the right side;
along with concrete cracks at height of 120mm from column top; then test stopped. The column buckling starts
at 25 tons Load; and 0.625 m.t bending moments; accordingly the failure load is 25 tons and the failure mode is
buckling of flange plates associated with concrete crushing. The failure load is decreased by 5 tons than
specimen P-1 and this is due to using longer column (H/d=8); the flange buckling happened faster due to the
usage of longer column Figure (12); the failure mode is similar to previous studies failure mode ; column flange
buckling starts and hence concrete cracks appears. When buckling occurred the flange steel plate leaves the
concrete surface thus the confinement of the concrete no longer exists thus the concrete acts alone and cracks
appears Figure (13).
Columns P-5

Specimen P-5 is used to study the effect of the third parameter the column height to depth ratio but with (H/d =
10) on the behavior of PECBC. Load was applied and increased gradually from 5 tons up to 15 tons; readings
and observations are recorded every 5 ton. Then loads increased from 15 tons to 24.5 tons gradually; readings
and observations are recorded every 1 tons. Up to 24 ton loading there are no observations of any flange
buckling or concrete crushing. At 24.5 ton load; column flange buckling occurred at height of 150 mm (0.15H)
from column bottom at the right side Figure (14); along with concrete cracks at height of 200 mm from column
top Figure (15) and bottom; then test stopped. The column buckling starts at 24.5 tons Load; and 0.61 m.t
bending moments; accordingly the failure load is 24.5 tons and the failure mode is buckling of flange plates
associated with concrete crushing; the failure load is decreased by 5.5 tons than specimen P-1 and this is due to
using longer column (H/d=10); which is similar to P-4 with only difference of 0.5 t which is due to increasing
the column height to depth ratio from 8 to 10. The flange buckling happened faster due to the usage of longer
column; the failure mode is similar to previous studies failure mode; column flange buckling starts and hence
concrete cracks appears. When buckling occurred the flange steel plate leaves the concrete surface thus the
confinement of the concrete no longer exists thus the concrete acts alone and cracks appears.
Bare Steel and Reinforced Concrete Specimens
Four Bare steel columns measuring 100x100 in cross section were constructed two of them with height 500mm,
one of 800mm height and one of 1000mm height; with specimen properties as shown in table 2 same properties
as the PECBC; and five reinforced concrete columns measuring 100x100 in cross section were constructed,
three of them with height 500, one of 800 height and one of 1000mm height; with specimen properties as shown
in table 3 below. The longitudinal reinforcement used was with same yield strength and area as of the steel
plates used for the PECBC and the steel columns. All the specimens were tested using the same machine and
under the same conditions as the PECBC specimens; loading was applied and results were recorded. Figure (16)
& (17) shows the steel and RC specimens after testing.
Table 2. Bare Steel Specimens
Specimen 2b (mm) d (mm) t (mm) S (mm) e (mm) H (mm) Fy (Kg/cm2
)
S-1 100 100 2.0 100 25 500 2350
S-2 100 100 2.0 50 25 500 2350
S-4 100 100 2.0 100 25 800 2350
S-5 100 100 2.0 100 25 1000 2350
Table 3. Reinforced Concrete Specimen
Specimen b (mm) d (mm) RFT (mm)
S
(mm)
e
(mm)
H
(mm)
fcu
(Kg/cm2
)
Fy
(Kg/cm2
)
C-1 100 100 12Dia 8.0 100 25 500 350 2400
C-2 100 100 12Dia 8.0 50 25 500 350 2400
C-3 100 100 12Dia 8.0 100 25 500 300 2400
C-4 100 100 12Dia 8.0 100 25 800 350 2400
C-5 100 100 12Dia 8.0 100 25 1000 350 2400
PECBC Testing Results
Failure mode for the five specimens is nearly the same; Column flange buckling happens thus separation
between the steel flange plate and the concrete surface happens; thus concrete is no more confined by the steel
plates and resist the load alone thus concrete cracks appears and hence concrete crushing; the failure mode is
typical to previous experimental studies happened for concentric PEC columns testing. Column’s flanges
buckling and concrete crushing. Column load capacity differs for each specimen and it is obvious that the
highest column capacity is specimen P-2 with closer link spacing S=d/2 and column height = 5 d and concrete
compressive strength of fcu = 350 kg/cm2; while specimen P-1 comes the second one as the link spacing s=d
with column height = 5 d and concrete compressive strength of fcu= 350 kg/cm2; then comes specimen P-3 with
link spacing = d with column height = 5 d but with concrete compressive strength of fcu= 300 kg/cm2 Figure;
then specimen P-4 with link spacing s=d and concrete compressive strength of fcu= 350 kg/cm2 but with
column height = 8d; and the last one is specimen P-5 with link spacing s=d and concrete compressive strength
of fcu= 350 kg/cm2 but with column height = 10d. Table 4 below shows the specimen failure load.

Table 4. PECBC Specimens Failure Load
Specimen
No.
PECBC Specimen Failure
Load
Normal
Load (t)
Bending
Moment (m.t)
P-1 30 0.75
P-2 32 0.8
P-3 28 0.7
P-4 25 0.625
P-5 24.5 0.6125
Conclusion
The behavior of partially encased composite beam column was assessed using experimental testing
The Column load capacity differs for each specimen; the highest column capacity is specimen P-2 with closer
link spacing S=d/2 and column height = 5 d and concrete compressive strength of fcu = 350 kg/cm2; while
specimen P-1 comes the second one as the link spacing s=d with column height = 5 d and concrete compressive
strength of fcu= 350 kg/cm2; then comes specimen P-3 with link spacing = d with column height = 5 d but with
concrete compressive strength of fcu= 300 kg/cm2but; then specimen P-4 with link spacing s=d and concrete
compressive strength of fcu= 350 kg/cm2 but with column height = 8d; and the last one is specimen P-5 with
link spacing s=d and concrete compressive strength of fcu= 350 kg/cm2 but with column height = 10d.
PECBC capacity is almost triple the steel columns specimens; hence the addition of concrete to the steel
columns to cover the web plate; enhanced the column behavior due to the confinement of the steel column
creating the PECB; the concrete and the steel section acted compositely due to the existence of the steel links
which acted as shear connectors. The column gained the higher capacity while still gaining the advantage of
steel structure column as the flanges are exposed for easier beam column connection; on the other hand using
slender steel plates gives the advantage of using light sections thus more lesser crane capacity and less project
cost.
PECBC capacity is less than the reinforced concrete beam column capacity by about 17 to 27 %; hence for the
same column price (as both series had the same concrete and steel volume) the RC columns had more column
capacity by average 22% over the PECBC; but still had the disadvantage for longer construction durations and
more complicated fabrication process.
The 22% less capacity can be gained by either using higher concrete strength or thicker steel plates for the
PECBC which can be done with minimum cost and accordingly have the same RC column capacity and the
advantages of the PECB Columns.
Notations
PECBC = Partially Encased Composite Beam Columns
RC = Reinforced Concrete
b = Half flange width
d =Specimen depth
t = Plate thickness
s = Vertical link spacing
fcu= Concrete cubic compressive strength
Fy= Steel yield strength
H = Column height
Puexp.= Experimental failure load
CISC= Canadian Institute for Steel Construction
L= Load
SG= Strain Gauge
Lin Pot= Linear Potentiometer
References
[1.] Euro Code 4 Part 1 clause 4.8 Composite Columns.
[2.] CISC Canadian Institute of Steel Construction clause 18.3 Partially Encased Composite Columns.
[3.] AISC-LRFD Manual of Steel Construction American Institute Of steel Construction Load and
Resistance Factor Design third Edition.
[4.] R. Tremblay, B. Massicotte, I. Fillion and Maranda (1998) "Experimental study on the behavior of
partially encased composite columns made with light welded H-steel shapes under compressive axial
loads" Proc., 1998 SSRC Annual Technical Meeting, Atlanta, 195-204.

[5.] Ghosh & M. Begum “Simulations of partially encased composite columns under concentric loading
using equivalent steel section” 4th Annual Paper Meet and 1st Civil Engineering Congress, December
22-24, 2011, Dhaka, Bangladesh.
[6.] Brent S. Pricket and Robert G. Driver “Behavior of PECC made with high performance concrete”
Structural engineering report No.262; University of Alberta Department of civil and environmental
engineering; Canada.
[7.] Mahboba Begum, Robert G Driver and Alaa E Elwi “Finite element modeling of partially encased
composite columns using dynamic explicit method” 326 / Journal of Structural Engineering ASCE /
March 2007.
[8.] Saima Ali and Mahboba Begum “Behavior of partially encased slender composite columns in eccentric
loading” 4th Annual Paper Meet and 1st Civil Engineering Congress, December 22-24, 2011, Dhaka,
Bangladesh.
[9.] Christine la Casse “Experimental and analytical study for PECC using high performance concrete and
fiber concrete” Civil and Geological Mining Department - Montreal University - Canada; Ph.D. Thesis
2011.
Figure (3) P-1 Flange Bucklin Figure (4) P-1 Concrete Crack Figure (5) P-1 Web Buckling
Figure (6) P-2 Flange Buckling Figure (7) P-2 Concrete Cracks Figure (8) P-2 Failure zones
Figure (9) P-3 Flange separation Figure (10) P-3 Flange Buckling Figure (11) P-2 Failure zones

Figure (12) P-4 Flange Buckling Figure (13) P-4 Concrete Cracks
Figure (14) P-5 Flange Buckling Figure (15) P-5 Concrete Cracks
Figure (16) Bare Steel Specimens after Failure

Figure (17) Reinforced Concrete Specimens after Failure

Experimental Testing Of Partially Encased Composite Beam Columns

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